On the spatial dependence of low-degree solar p-mode frequency shifts from full-disk and resolved-sun observations

We have analyzed low angular degree (low-l) solar p-mode frequency shifts extracted from two types of observations, both made by instruments on board the ESA/ NASA Solar and Heliospheric Observatory satellite during a period that covers the rising phase of activity, cycle 23 ( 1995 - 2002). The first are full-disk (Sun-as-a-star) averages made in Doppler velocity by the Global Oscillations at Low Frequency spectrophotometer; the second are Doppler velocity observations made with high spatial resolution by the Michelson Doppler Imager. We compare the eigenfrequency shifts from both sets of data and find that they are consistent at the level of precision of the observations. Furthermore, the sizes of the shifts uncovered for different mode components are found to scale in proportion to the corresponding spherical harmonic components of the observed line-of-sight surface magnetic field, with the sectoral mode components showing (as expected) the largest shifts.